Contact finger for electric machines and apparatus



June 27, 1933. 4 G; PEDRAZZO 1,915,948

CONTACT FINGER FOR ELECTRIC MACHINES AND APPARATUS Filed July 21, 1930 2 Sheets-Sheet 1 I N VEN TOR.

67b Vcmr; z lgdraz 20 A TTORNEY.

June 27, 1933. PED'RAZZQ 1,915,948

CONTACT FINGER FOR ELECTRIC MACHINES AND APPARATUS Filed July 21, 1930 2 Sheets-Sheet 2 2&-

Invenfor:

Giovanna .Peairazzo,

Patented June 27, 1933 UNITED STATES PATENT orslcs GIOVANNI PEDRAZZO, OF IBIEBLA, ITALY GOHTACT FINGER- FOR ELECTRIG MACHINES AND APPARATUS Application filed July 21, 1930, Serial No. 469,511, and in Italy July so, 1929.

My invention relates to a new and improved form of contact fingers for electric machines, and similar apparatus.

More particularly, my invention is designed to ensure a proper operation of the contact fingers, in addition to reducing the production costs.

Among other advantages, my invention is characterized in its facility of installing the m contact finger, in combination with its holder, in an electric apparatus, etc., an operation which can be performed by any fitter. With my construction there is no need of adjusting the finger of contact surface relative to the movable part of the said electric apparatus.

In addition, my invention possesses the advantage that the pressure of the spring which biases the contact finger, in combination with the devices which will be described here- 7 inafter, has a tension only suiiicient to ensure the proper contact of the finger or contact surface against a movable part of the electric apparatus; since as a consequence the spring has no other load, it can be comparatively small, and therefore extremely sensitive. The

sensitive pressure of the spring itself therefore permits the finger, in combination with the said devices, to contact over its full contact surface against the said movable part of the electric apparatus, and to be maintained in the position of good contact required by the said movable part. It results from the foregoing that the full contact surface of the finger will always follow the oooperating surface of the movable part of an electric apparatus, with which the contact finger is designed to cooperate.

Still further, my. invention permits the ade quate regulation ofthe position of the contact finger relative to a movable part of the electric apparatus, by any fitter. The finger automatically adapts itself throughout its contact surface, against the said movable part and ensures perfect contact even in the instance that the finger or contact surface is not perfectly parallel to the said movable part: viz: the contact finger adapts itself in parallel relation against the said movable part, and maintains such position. The operation of the movable part of the electric apparatusprovided with contact fingers according to my invention is very sensitive; that is, the workman operating the said movable part is required, as a result of my constructlon, to overcome only a minimum of operating force.

It is readily understood that the good contact ensured by my invention permits a uniformity in operation of the machine, as well as considerably reduced operating cost as compared with the prior art devices. 7

My invention is disclosed, merely by way of example, as consisting of three distinct features, which will be better explained by reference to the figures of the drawings, in which:

Fig. 1 shows schematically, in operating position, an example of contact fingers, in side elevation, partly insection, fully illustrating the three elements forming the object of my invention, which elementsare'shown in section together with the cooperating parts;

fFFig. 21 shows a plan view of the apparatus 0 1g.

Fig. 3 shows schematically in section, on

the line AA of Fig. 1, an example of one 'of the elements according to my invention;

Fig. 4 shows schematically in section, on the line BB of Fig. 1, an example of another element (rear s1de,opposite to the con- 8 tact), according to my invention; I

Fig. 5 shows schematically .in section, on the line C-C, of Fig. 1, an example of still another element (central), according to my invention; and

Figs. 6 and 7 are vertical sections through still another constructional embodiment of my invention; while i I Figs. 8 and 9 disclose, in vertical section, yet another modification thereof.

; Referring to Fig. 1 the holder 1 carries the contact finger 10, while the clip 2 serves, by means of the bolts 3, to fix the holder 1 on the insulating bar 4. Flexible cables are shown at 5, having a terminal plug soldered at each end, serving to transmit the current from the holder 1 to the contact finger 10, the said cables being formed by flexible wires and beingiplaced in such manner as to avoid undesirable mechanical impediments to the operating movement of the contact finger; a bolt 6 serves to fix the cables 5 on one side and also to fix the strand conductor (not shown) transmitting the current to the holder 1. The contact 7 by means of the bolt 8, is fixedto the finger 10, which is shown in operating position against the contact surface of the movable part 9.

A ball or spheroidal journal 11 is fixed to the finger 10 by means such as a nut-12, which in combination with the corresponding groove 13 of the holder 1, forms one of the constructional forms of the left-most or front device of Fig. 1 according to my invention, and is bettenshown in Fig. 3, in its operating position against a contact (of'a movable part not shown) which is not parallel to the contact 7 of the finger 10. The said front device prevents the contact finger 10, 7 from deviating from its operating direction and also 7 supports the contact finger itself when in its rest position in the holder 1 by means of the extremity of the spheroid 11 which rests in the bottom of the groove 13 of the said holder 1, thus supporting the finger adjacent its front part. Hence it follows that, in the said front device, formed by the said ball journal (or spheroid) and by the said corresponding groove, the spheroid 11 can roll in a sliding fashion fnom right to left and vice versa, within the walls of the groove 13 of the holder 1 during which the finger 10, 7 (in its operating movement) does not encounter any undesirable mechanical impediments.

'A ball or spheroidal journal 14 is shown as fixed to the finger 10 by means such as a nut 15, which nut, in combination withthe corresponding cavity 16 of the holder 1, forms one of the constructional forms of the rightmost or rear device (the side opposite to the .contact) according to my invention, and is better shown in Fig. 4, in operating position against a contact of a movable part not shown, which contact is not parallel to the contact 7 of the finger 10. The said device '14. 15, 16 serves to support the rear extremity of the finger 10. 7 in the holder 1 by means of the snheroid'14 resting in the cavity 16 of the holder 1. It follows, therefore, that in the said rear device formed by the said ball or spheroidal journal and by the said corresponding cavity, the spheroid 14, which can roll slidingly in the corresponding cavity 16 of the holder 1. permits the contact finger 10, 7 in its operating movement, to accomplish freely a ball and socket joint movement without encountering any undesirable mechanical impediments, the center of the spheroid 14 forming the center of the joint.

The nut 15, which fixes the spheroidal jour- I nal 14 in the finger 10 also serves to fix the terminal plug of the cables 5, transmitting the current from the holder 1 to the finger 10.

. A journal 17 is fixed at one end to the holder 1, which journal serves to carrythespring 20 which biases the finger 10, and also carries the special nut 21 which serves to regulate the pressure of the spring 20 and to release the same. Still further, the said journal 17 carries, in combination between the spring 20- finger 10 is not parallel to the holder 1, due

to the fact that the contact 7 shown in Fig. 1, is located against a movable part (not shown) which is not parallel to the said holder 1. The said convex body 18, applied against the finger 10, always follows the finger throughout its operating movement. To permit the finger 10 a certain freedom of movement or play with respect to the journal 17, a hole of larger diameter than that of the journal 17 is provided in the finger 10 and in the body 18. The concave body 19 moves about the journal 17, in combination with the spring 20, by means of the reciprocating stroke of.

the finger 10, similar to a movable, hollow cylindenmovingon a fixed' piston. It follows thereforethat the convex surface of the body 18 can slide in the ball and socket joint movement in the concave surface of the body 19, so that the contact finger 10, 7, during its operating movements, does not encounter any undesirable mechanical impediments, and automatically in combination with the pressure or friction exerted by the spring, remains in contact with the movable part 9, even if the latter is not perfectly parallel to the holder 1. In-the drawings, Fig. 1 and Fig. 5, the convex body 18 is shown as existing separately. It is evident however that if desired, it can also be constructed solidly with the contact finger 10 (Figs. 6 and 7). It must be noted that the said central device, according to my invention, can be placed in a number of different ways. In addition to the use of a tensioned spring instead of a compression one, the user can also construct the journal 17 in such manner as to move freely in a bearing 24 fixed to the holder 1, (Figs. 69) and can fix the concave body 19 to one of its extremities and the nut 21 at the other extremity (Figs. 8-9), in order to obtain the same result, with the difference that the sprlng has thus become tensioned instead of under compression. In such case the journal 17, will, in addition to the body 19 and the body 18, be interposed between the spring and the only that between'the device which either presses or pulls the contact finger a body with concave surface and a body with convexsurface are interposed, which bodies can slide one in the other, in a ball and socket joint movement.

It is readily understood that once the broad aspects of my invention have been disclosed, numerous modifications and adaptations thereof, falling within the scope of thev the rear or supported end of the contactfinger is mounted, the said pivot comprising an approximately ball-shaped member on the finger, a support having a cavity adapted to receive the said ball-shaped member, a spring device, Washershaving concave and convex surfaces mounted about the central part of the finger, and interposed between the finger and the said spring device, said ball-shaped member and said concave-convex washer providing for universal movement of the contactfinger and for the automatic adjustment of its free end transversely of the cooperating contact surface.

:2. in combination, a contact finger for electric machines and apparatuses having a free front end and a supported rear end, a cooperating contact surface with which the front end or free extremity of the'contact finger is adapted to engage, a pivot on which the rear or supported end of the contact finger is mounted, the said pivot comprising an approximately ball-shaped member on the finger, a support having a cavity adapt ed to receive the said hall-shaped member, a spring device, a second approximately ballshaped member mounted on the finger, the said support having a corresponding groove within which the second ball-shaped mom her is received, for further guiding the finger in relation to the support, washers having concave and convex surfaces mounted about the central part of the finger and interposed between the finger and the said spring device, said ball-shaped member and said concave-convex washers providing for universal movement of the contact finger and for the automatic adjustment of its free end transversely of the cooperating contact surface.

, 3. In combination, a contact finger for electrical apparatus having a free front end transversely of the cooperating contact surfaces 4. In combination, a contact finger for electrical apparatus having a free front end and a supported rear end, a cooperating contact surface: with which the front end or free extremity of the contact finger is adapted to engage, an aperture extending through said contact finger, a spring pressed shaft extending through said aperture and seating inthe supporting member for said contact finger, cooperating concave and convex surfaces on said contact finger about said shaftv and movable relatively to each other as a ball and socket joint, the spring of said shaft tending to maintain said surfaces in engagement, the said surfaces providing for universal movementiof the contact finger and for automatic adjustment of its free end transversely of the cooperating contact surface.

In testimonvwhereof I have signed my name to this specification.

erovaivur rnnaazzo. 

